Modern processors present in devices such as computers, smartphones, etc. have capabilities allowing them to adjust the clock frequency depending on the processing load. Also, multi-core processors allow for some of the cores to perform calculations at regular speeds while others are kept in a low-powered sleep mode until their contribution is required by the overall load of the system (for example, in the Tilera TileGX family). Network processors that take care of the packet forwarding function in switches and routers are also based on multicore designs (for example, the Cavium Octeon and the Xelerated HX). However, it was not possible to determine what power saving features is incorporated in these network processors, based solely on publicly available information.
The P802.3az standard proposal, based on the investigation started by the IEEE 802.3 Energy Efficient Ethernet Working Group, introduces three power states for the Ethernet PHY: full, low power idle, off. The Energy Efficient Ethernet workgroup at IEEE is evaluating technologies that would allow Ethernet bridges to reduce their power consumption by introducing a low-power idle mode for the PHY component when there is no traffic to be sent. Low power modes for Ethernet controllers (that is, allowing for power savings beyond the PHY chip) were suggested by D. Koenen in 2007, Potential Ethernet Controller Power Savings, www.ieee802.org/3/eee_study/public/may09/koenen—1—0507.pdf.
The Broadband Forum TR-202, TR-202 ADSL2/ADSL2plus Low-Power Mode Guidelines, Broadband Forum, February 2010 defines three power states for ADSL equipment (L0 full power, L2 low power, L3 no signal with the transceiver either powered or unpowered).
Academic proposals such as the ClickCAM research proposes techniques to reduce the power consumption of particular chips on a switch/router linecard (the TCAM, in this particular case), Exploring Router Power Performance Tradeoffs Using Click.
An overall solution for energy minimization at the network node was proposed by Bolla et al, GreenSim: An Open Source Tool for Evaluating the Energy Savings through Resource Dynamic Adaptation, Raffaele Bolla et al. The authors constructed an energy consumption model for a PC-based multicore router and devised a method to optimize the energy consumption taking into account the traffic passing through the device. The solution proposed by Bolla et al. relies on ACPI calls that enable the equipment to switch between power conservation modes. Such a solution is clearly limited to routers based on multi-core processors that support ACPI calls. Also, their model includes a simple node-based traffic estimator. However, in practice, such a traffic estimator is quite energy-hungry to operate on each network node (CPU time and memory occupancy). Also, such a traffic estimator is complicated at the network node level to implement in a carrier network that supports multiple classes of services.
In US2009089601 a power saving mechanism on GMPLS controlled networks is described. The consumption is reduced by cutting power consumption on spare paths that are not normally used. To achieve power consumption reduction, in the path setting process, a path is calculated while taking the power saving capability of each interface into account, and the applicable interface is set to the power-saving state when setting the spare path. When the spare path was set to the operating state, then the power-saving state on the applicable interface was canceled so that interface could operate normally. The power reduction strategy described is clearly limited and only considers shutting down paths that are not in use. A finer granularity of power state updates is required. Further, not only GMPLS-based networks must be considered.
The Resource Reservation Protocol (RSVP) is a network-control protocol that enables Internet applications to obtain differing qualities of service (QoS) for their data flows. Such a capability recognizes that different applications have different network performance requirements. There exist extensions to RSVP, such as RSVP-TE which allow the operator to traffic engineer the network.
On the radio network side, the power saving features in a base station is discussed at length in WO2009031955. Of particular interest to is the mention that a base station has several transmitters (TRX), and using power-management algorithms some of them could be put temporarily in a stand-by mode thus saving energy.
In summary, according to prior art, network nodes include capabilities that allow reducing the power consumption depending on the level of traffic and/or operator policies. Known power saving schemes includes various degrees of flexibility with respect to the amount of power savings to be expected. For multi-core network processors, it is possible to reduce the clock speed and shut down individual cores (Tilera GX being an example). Ethernet PHY chips will support P802.3az features and potentially operate in three different power modes (on, idle, off). For other components, such as the TCAMs, academic contributions such as ClickCAM suggested ways to build them in ways that enable energy-efficient operating modes.
The Metro Ethernet Forum is working on a series of specifications that describe Ethernet connectivity services. Such Service Level Specifications include the specification of bandwidth profiles and support for protection switching features (MEF 6.1 describes Service Definitions, MEF 10.2 specifies Service Attributes). Ongoing work in IETF supports the automated provisioning of such services over GMPLS networks (draft-ietf-ccamp-gmpls-mef-uni).
The authors of JP 2009147615 disclose a method for controlling the energy consumption of the router based on bandwidth reservations made via messages transmitted with the RSVP protocol. The authors describe a system that is able to reduce the clock frequency of the chip and control the power supply voltage provided to the chips in accordance to pre-defined resource reservations. The solution proposed by JP 2009147615 is addressing only pre-reserved resources and it does not take into account that those resources might be used at less than the maximum capacity during normal system operation. As such, the solution proposed is inefficient with respect to the actual energy savings that could be achieved during operation. Also, presented is an individual node-centric view and does not extend or correlate the savings at a network level. The solution presented does not allow the operator to control what level of savings should be achieved by each node. In terms of practical implementations, the suggestions to reduce the clock frequency and the power supply voltage for the packet processing unit cover only some of the potential cases, and are by no means universal applicability. For example, Ethernet PHY chips supporting P802.1az would be able to shut down parts of the chip (except the low power idle circuitry) while not necessarily being able to control neither the clock frequency nor the power supply voltage. Also, the solution disclosed does not make it very clear what happens when a certain network port supports multiple resources which would be reserved through unrelated RSVP sessions.
Anecdotic evidence suggests that switches and routers operate at maximum capacity regardless on the traffic generated by the services being supported at a given moment in time. Technology exists that would allow individual components on the switch/router linecard to be switched off temporarily, or put in low power consumption modes when there is no traffic. However, such individual solutions are unlikely to optimize the overall power consumption of the node or the path, and are likely to operate in an uncoordinated way which might cause problems (such as packet loss, or increased transmission times).
The solutions according to the prior art are thus associated with a plurality of drawbacks.